It is becoming more and more common to use multi-chamber medicament containers in medicament delivery devices such as injectors. The reason for this is that the medicament can be stored for much longer time periods without being degraded in comparison with medicament dissolved in some liquid.
Thus the medicament and the liquid are kept in different compartments in the medicament container and are mixed just before use by moving a dividing wall or stopper such that the compartments can communicate with each other.
However, the multi-chamber medicament containers entail more handling steps before a dose of medicament can be injected in that the plunger rod of the injector has to move the stopper or stoppers of the medicament container in order to initiate the mixing.
Another feature of many medicament delivery devices and in particular injectors is the attachment of a medicament delivery member, in particular an injection needle to a medicament container and then how to avoid unintentional needle sticks. Document WO2010/000559 discloses a medicament delivery device utilizing a multi-chamber medicament container where the mixing is obtained by rotating a medicament container holder, positioned in the proximal housing part, into a distal housing part whereby the stopper of the medicament container is moved against a plunger rod. In the initial position the proximal end of the medicament container is protruding beyond the proximal housing part, where the latter also acts as a needle shield, such that a medicament delivery device can be attached to the medicament container holder. When the mixing has been performed, the medicament delivery member is drawn into the proximal housing/needle shield. The needle shield is now used for actuating the device in that when a penetration is performed, the needle shield is pushed in the distal direction, whereby it triggers an auto-injection sequence. Thus the needle shield assembly extends almost to the distal end of the device in order to be able to actuate the injection.
However, for some devices it is neither necessary nor desirable to have so many components and functions since they tend to make the devices more complex and more expensive. Also the holding of the device during mixing may be performed with one hand rather close to the proximal end of the device instead of the distal end of the device. There is thus room for development of medicament delivery devices.